1. Field of the Invention
The present disclosure relates to gas turbine engine vanes. More specifically, the present disclosure relates to an insertable impingement rib assembly used for cooling gas turbine engine vanes.
2. Description of Related Art
Gas turbine engine vanes are used within the hot gas stream to direct the stream onto the rotating blades of the engine from which power is extracted. The conventional process used to fabricate a turbine vane is to cast the part. While the casting process yields a high quality product, it is costly and time consuming. The airfoil portion of the turbine vane is prone to overheating because of the extremely high temperatures that it is exposed to and making repairs to damaged airfoils can be expensive and impractical. Presently, it is not conveniently possible to adjust the amount of air flow being supplied to some of the impingement rib feed cavities by way of airfoil cooling passages without expending great amounts of time and money. Turbine vanes must be cooled to maintain structural integrity and one effective method of cooling is impingement cooling.
Turbine airfoils have ribs that are integrated, or permanently cast into the turbine vane casting configuration. The impingement ribs have crossovers that form impingement holes. Cooling air is provided to flow through the impingement holes in the impingement rib. The impingement rib functions as a cooling mechanism to tailor and/or tune the air flow through the turbine vanes. The impingement holes function to pressurize the air flowing behind them so that the air traveling through the holes is cooler.
Conventional turbine vane casting configurations are such that accurate hole sizing at the start of the casting process is of great importance. Once the core cylinders are leached out, fixed holes that are a product of the die remain. Impingement holes must be sized before the casting process commences and any holes that are sized improperly can adversely affect the life of the part. Current technology and casting tools makes the modification of impingement hole sizes laborious, difficult and time consuming because any necessary changes to hole sizes requires the casting tools to be modified. Additionally, the casting of impingement holes may result in substantial scrap, which leads to lost time and higher costs.
A further problem with the current casting configuration of a turbine vane is timing. As development programs are forced into shorter schedules, minimal time is allowed for engineering iterations that affect the casting of turbine vanes. This is because the lead-time associated with the creation of casting tools is fixed. The current casting configuration is also flawed in that the lifetime of the parts is sacrificed if impingement holes are sized improperly.
Accordingly, there is a need for a casting configuration of a turbine vane that provides flexibility to adapt to changing conditions and removes upstream guesswork. There is a further need for a universal casting that can receive an easily alterable and easily created insertable impingement rib upon assembly that will be more cost effective and will increase the lifetime of the turbine vane and its components.